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| Paper: |
Solar-Cycle Related Changes at the Base of the Convection Zone |
| Volume: |
416, Solar-Stellar Dynamos as Revealed by Helio- and Asteroseismology: GONG 2008/SOHO 21 |
| Page: |
477 |
| Authors: |
Baldner, C. S.; Larson, T. P.; Basu, S. |
| Abstract: |
Solar oscillation frequencies are known to change with solar activity. We repeat earlier work examining these changes to high precision with newly analyzed data from the MDI instrument. In addition to the well-documented changes in solar normal mode oscillations with activity as a function of frequency, which originate in the surface layers of the Sun, we find a small but statistically significant change in frequencies with an origin at and below the base of the convection zone. This change is very tightly correlated with solar activity. If we interpret the change in frequencies as being caused by change in sound speed, we find that at r = (0.712 +0.0097 -0.0029) Rsun the change in sound speed is Δc²/c² = (1.28 ± 0.29) × 10-4 between the highest and lowest activity data. This is slightly larger than the results from the old data, and implies a change in field strength of 390 kG at the base of the convection zone. In addition, we use the splitting coefficients to examine the latitudinal structure of these changes and find changes in sound speed that are correlated with surface activity for r ≥ 0.9 Rsun. |
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